1. Field of the Invention
The invention relates to a control apparatus/method of a vehicular driving apparatus comprising an engine and a second driving power source that assists the engine in the output of driving power. More particularly, the invention relates to a technology of controlling the load state of the engine in order to curb degradation of the emission gas.
2. Description of the Related Art
Vehicles equipped with an emission gas recirculation device, a so-called EGR device, which refluxes a portion of the emission gas of an engine, such as a diesel engine or the like, to the intake system, that is, recirculates it to the intake system in order to reduce the amount of emission of NOx (oxides of nitrogen) are well known. See, e.g., Japanese Patent Application Laid-Open Publication No. JP-A-2004-197703; Japanese Patent Application Laid-Open Publication No. JP-A-2004-204778; and Japanese Utility Model Application Laid-Open Publication No. JP-U-6-4344. In such vehicles, an EGR valve is provided in an EGR passageway that connects an exhaust passageway and an intake passageway of the engine. The amount of opening/closure of the EGR valve is controlled in accordance with the state of operation (state of load) of the engine so as to adjust an emission gas reflux amount (emission gas recirculation amount, or EGR amount) which is the amount of emission gas refluxed, or an emission gas reflux rate (emission gas recirculation rate, or EGR rate), which indicates the emission gas reflux amount with respect to the amount of inflow air.
However, if the intake negative pressure decreases as the engine shifts to a higher-load operation state, the EGR rate may decrease so that the NOx (oxides of nitrogen) emission amount cannot be reduced. Moreover, if the emission gas recirculation (EGR) device is required to operate in a high engine load region, PM (particulate matter) in the emission gas may increase; that is, there is a possibility that performance of EGR may be substantially impaired in the high engine load region.